1. Genetics: The Heritability of Intellectual Ability
David Kerr

2. Nature vs Nurture

3. What is heritability?
Heritability looks at what variance of a trait throughout the population is due to genetic factors (I.E. nature)
Other factors that impact the prevalence of traits are characterized as environmental factors (I.E. nurture)
Some traits have high heritability, whereas others are highly impacted by the environment

4. Why test intelligence and not physical ability?
Intelligence is less conditional on physical dimensions
Even playing field makes it easier to study differences
Standardized tests are in place for measuring and testing intelligence
5’9”
128lbs
6’5”
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5. From: The Cambridge Handbook of Expertise and Expert Performance
The Influence of Experience and Deliberate Practice on the Development of Superior Expert Performance
From: The Cambridge Handbook of Expertise and Expert Performance
(K Anders Ericsson, 2006)

6. Ericsson on Practice
Practice is necessary and what takes everyday performance to expert performance
Claiming that intellect is heritable does not challenge this
Merely suggests that some people are more predisposed to be able to achieve these expert levels of performance
K Anders Ericsson, 2006
P. 691
K Anders Ericsson, 2006
P. 687

7. Nature, Nurture, and Cognitive Development from 1 to 16 years: A Parent-Offspring Adoption Study
(Plomin et al., 1997)

8. Parent-offspring study model
Twenty year longitudinal study
Colorado Adoption Project
Institute of Behavioural Genetics
University of Colorado Boulder
Large sample size
490 total subjects
Multiple testing times
Matched pair control group

9. Parent-Offspring Study Findings
IQ heritability increased with age
In infancy and early childhood children mirrored their adoptive parents
By age 14 correlation between Adoptive Parent IQ and child IQ was at zero
Plomin et al., 1997
P. 444

10. Results in Specific Cognitive Abilities
Top Left: Verbal Ability
Top Right: Spatial Ability
Bottom Left: Speed of Processing
Bottom Right: Recognition memory
Plomin et al., 1997
P. 445
(Plomin et al., 1997)
P. 445

11. Application of Hierarchical Genetic Models to Raven
and WAIS Subtests: A Dutch Twin Study
(Rijsdijk, Vernon & Boomsma, 2002)

12. Dutch Twin Study Model Longitudinal Study Large sample size
194 Pairs of twins
Multiple testing times
Multiple Completed tests
Including tests for reaction time and nerve conductivity

13. Dutch Twin Study Results
High heritability in Verbal skills (VOC, VC & VIQ) Performance IQ and Full Scale IQ
Similar tests to those completed in the Parent-offSpring Study
Claim that there is little impact from environment
Rijsdijk, Vernon & Boomsma, 2002
P. 205

14. Future Research: What now?

15. Future Research Heritability of intellect and it’s impact on learning
“Hard work beats talent, when hard work doesn’t practice”
Test to see at what point the heritability advantage ceases to exist and those who are better practiced begin to exceed the natural abilities that the others have
Areas to test for heritability advantage
Spatial problem solving (mazes puzzles, tetris style spatial situations, Rubix Cube)
Memory (long and short term; audible, visual and factual)
Fine motor coordination activities (mirror tracing, reaction times)
These areas were selected because they are intellect-based problems that are solved in a physical space, as well as the fact that there can be strategies learned to aid in their completion, allowing for the acquisition of skill

16. References
Deary, I., Spinath, F., & Bates, T. (2006). Genetics of intelligence. European Journal of Human Genetics : EJHG, 14(6), doi: /sj.ejhg
Ericsson, K. A. (2006). The influence of experience and deliberate practice on the development of superior expert performance. In K. A. Ericsson, N. Chamess, P. J. Feltovich & R. R. Hoffman (Eds.), The Cambridge handbook of expertise and expert performance (1st ed., pp ). Cambridge, UK: Cambridge University Press.
Plomin, R., Fulker, D. W., Corley, R., & DeFries, J. C. (1997). Nature, nurture, and cognitive development from 1 to 16 years: A parent offspring study. Psychol.Sci., 8(6),
Polderman, T. J. C., Gosso, M. F., Posthuma, D., Van Beijsterveldt, Toos C E M, Heutink, P., Verhulst, F., & Boomsma, D. (2006). A longitudinal twin study on IQ, executive functioning, and attention problems during childhood and early adolescence. Acta Neurologica Belgica, 106(4),
Rijsdijk, F., Vernon, P. A., & Boomsma, D. (2002). Application of hierarchical genetic models to raven and WAIS subtests: A dutch twin study. Behavior Genetics, 32(3), doi: /A: